Power converter and UPS (Uninterrupted Power Supply) comprising same

Abstract

The invention provides a power converter and a UPS including the same. The power converter comprises a first power conversion module, a second power conversion module, a third power conversion module and a switch unit, and the switch unit is configured to enable a first end of the first power conversion module to be selectively and electrically connected to a first phase or a neutral line of a three-phase power supply. The first end of the second power conversion module is selectively and electrically connected to the second phase of the three-phase power supply or the positive electrode of the rechargeable battery, and the first end of the third power conversion module is selectively and electrically connected to the third phase of the three-phase power supply or the negative electrode of the rechargeable battery; the second power conversion module, the third power conversion module and the switch unit are configured to perform DC-DC conversion on direct current output by the rechargeable battery through the second power conversion module and the third power conversion module and then provide the direct current to the direct current bus, and balance the positive electrode and the negative electrode of the direct current bus through the first power conversion module.

Description

Technical Field

[0001] The present invention belongs to the field of power supplies, and particularly relates to a power converter and an uninterruptible power supply (UPS) including the power converter. Background Art

[0002] The UPS is used to instantaneously switch to providing continuous power to a load by a backup power supply (such as a rechargeable battery) under abnormal conditions of the main power supply (such as the municipal power grid) to protect the load from damage caused by the interruption of the main power supply. The UPS generally includes an AC-DC conversion module (rectifier) for converting alternating current into direct current, a DC-AC conversion module (inverter) for converting direct current into alternating current, a backup power supply, a DC-DC conversion module (charger) for charging the backup power supply, and a DC-DC conversion module (battery converter) for performing DC conversion on the output voltage of the backup power supply.

[0003] When the main power supply fails, the UPS switches the system from running on the main power supply to running on the backup power supply, and when the main power supply resumes operation, it switches from running on the backup power supply to running on the main power supply.

[0004] With the continuous development of new energy (such as lithium batteries) and the continuous expansion of new energy application scenarios, more and more UPSs use new energy as the backup power supply, which also poses higher requirements for the backup power supply mode of the UPS. The existing UPSs usually use dedicated circuit modules to implement functions such as AC-DC conversion, DC-DC conversion, and DC bus balance, resulting in low circuit utilization, large volume, and high cost of the entire UPS. Summary of the Invention

[0005] Therefore, the object of the present invention is to overcome the above-mentioned defects of the prior art and provide a power converter, including:

[0006] A first power conversion module, which can be configured to implement AC-DC conversion, and a first end of the first power conversion module is configured to be electrically connected to the first phase or the neutral line of a three-phase power supply, and a second end is configured to be electrically connected to the DC bus;

[0007] A second power conversion module, which can be configured to implement AC-DC conversion, and a first end of the second power conversion module is configured to be electrically connected to the second phase of the three-phase power supply or a rechargeable battery, and a second end is configured to be electrically connected to the DC bus; and

[0008] A third power conversion module, which can be configured to implement AC-DC conversion, and a first end of the third power conversion module is configured to be electrically connected to the third phase of the three-phase power supply or a rechargeable battery, and a second end is configured to be electrically connected to the DC bus;

[0009] A switching unit configured to selectively electrically connect a first end of the first power conversion module to a first phase or a neutral line of the three-phase power supply, a first end of the second power conversion module to a second phase of the three-phase power supply or a positive electrode of the rechargeable battery, and a first end of the third power conversion module to a third phase of the three-phase power supply or a negative electrode of the rechargeable battery.

[0010] Wherein, the second power conversion module, the third power conversion module and the switching unit are configured to be able to perform DC-DC conversion on the direct current output by the rechargeable battery through both the second power conversion module and the third power conversion module and then supply it to the DC bus, and balance the positive and negative electrodes of the DC bus through the first power conversion module.

[0011] For the power converter according to the present invention, preferably, the second power conversion module and the third power conversion module respectively include an inductor, an upper bridge arm unit and a lower bridge arm unit, and are configured to perform DC-DC conversion through the upper bridge arm unit of the second power conversion module and the lower bridge arm unit of the third power conversion module.

[0012] For the power converter according to the present invention, preferably, the first power conversion module is a type-I three-level circuit, and the second power conversion module and the third power conversion module are double-boost circuits.

[0013] For the power converter according to the present invention, preferably, the double-boost circuit includes a first to fourth diode connected in series in sequence, a first and a second transistor connected in series with each other, and an inductor, wherein the negative electrode of the first diode is electrically connected to the positive electrode of the DC bus, the node between the positive electrode of the first diode and the negative electrode of the second diode is electrically connected to the first end of the first transistor, the node between the positive electrode of the second diode and the negative electrode of the third diode is electrically connected to the first end of the inductor, the node between the positive electrode of the third diode and the negative electrode of the fourth diode is electrically connected to the second end of the second transistor, the positive electrode of the fourth diode is electrically connected to the negative electrode of the DC bus, the node between the second end of the first transistor and the first end of the second transistor is electrically connected to the neutral line, and the second end of the inductor is electrically connected to the three-phase power supply or the rechargeable battery through the switching unit.

[0014] For the power converter according to the present invention, preferably, the type-I three-level circuit includes a first to a fourth transistor connected in series in sequence, a first and a second diode connected in series with each other, and an inductor. Among them, the first end of the first transistor is electrically connected to the positive pole of the DC bus, the node between the second end of the first transistor and the first end of the second transistor is electrically connected to the negative pole of the first diode, the node between the second end of the second transistor and the first end of the third transistor is electrically connected to the first end of the inductor, the node between the second end of the third transistor and the first end of the fourth transistor is electrically connected to the positive pole of the second diode, the second end of the fourth transistor is electrically connected to the negative pole of the DC bus, the node between the first diode and the second diode is electrically connected to the neutral line, and the second end of the inductor is electrically connected to the three-phase power supply or the neutral line through the switching unit.

[0015] For the power converter according to the present invention, preferably, the output terminals of the first phase, the second phase, and the third phase of the three-phase power supply are respectively grounded through capacitors.

[0016] For the power converter according to the present invention, preferably, it further includes a fourth power conversion module, which can be configured to implement DC-DC conversion. The first end of the fourth power conversion module is configured to be electrically connected to the rechargeable battery, and the second end is configured to be electrically connected to the DC bus.

[0017] For the power converter according to the present invention, preferably, the first end of the fourth power conversion module is electrically connected to the rechargeable battery through the switching unit.

[0018] For the power converter according to the present invention, preferably, the fourth power conversion module is a bidirectional DC-DC circuit.

[0019] For the power converter according to the present invention, preferably, the bidirectional DC-DC circuit includes a first to a third transistor and a first and a second inductor. Among them, the first end of the first transistor is electrically connected to the positive pole of the DC bus, the node between the second end of the first transistor and the first end of the second transistor is electrically connected to the first end of the first inductor, the node between the second end of the second transistor and the first end of the third transistor is electrically connected to the first end of the second inductor, the second end of the third transistor is electrically connected to the negative pole of the DC bus, the first end of the first inductor is configured to be electrically connected to the positive pole of the rechargeable battery, and the first end of the second inductor is configured to be electrically connected to the negative pole of the rechargeable battery.

[0020] The present invention also provides an uninterruptible power supply, including:

[0021] The power converter according to the present invention,

[0022] An inverter, electrically connected to the DC bus of the power converter; and

[0023] A rechargeable battery, whose output terminal is electrically connected to the switching unit of the power converter.

[0024] Compared with the prior art, the power converter of the present invention multiplexes the rectifier bridge arm as the battery conversion bridge arm and the balance bridge arm, greatly improving the circuit utilization rate and the battery power supply efficiency, and reducing the volume of the power converter and the cost. Description of the Drawings

[0025] The following further describes the embodiments of the present invention with reference to the drawings, where:

[0026] Figure 1 Is a schematic block diagram of a power converter according to an embodiment of the present invention;

[0027] Figure 2 Is the circuit topology of a power converter according to an embodiment of the present invention;

[0028] Figure 3 And Figure 4 Respectively show the current paths of the power converter according to the embodiments of the present invention in the mains mode and the battery mode;

[0029] Figure 5 Is a structural block diagram of a UPS according to an embodiment of the present invention; and

[0030] Figure 6 Is a structural block diagram of a UPS according to another embodiment of the present invention. Detailed Description of the Invention

[0031] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further details the present invention through specific embodiments with reference to the drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] Figure 1Schematic block diagram of a power converter according to an embodiment of the present invention. The power converter includes a first power conversion module 101, a second power conversion module 102, a third power conversion module 103, a first switch module 104, and a second switch module 105. The first switch module 104 is arranged between the first ends T1 and T2 of the first power conversion module 101 and the second power conversion module 102, the mains AC, and the rechargeable battery BT, and is configured to selectively electrically connect the first end T1 of the first power conversion module 101 and the first end T2 of the second power conversion module 102 to the mains AC and / or the rechargeable battery BT. The second switch module 105 is arranged between the first end T3 of the third power conversion module 103, the mains AC, and the neutral line N. The second ends T1', T2', and T3' of the first to third power conversion modules 101, 102, and 103 are configured to be electrically connected to the DC bus DC. Preferably, the power converter according to the embodiment of the present invention further includes a fourth power conversion module 106 and a fourth switch module 107. The fourth switch module 107 is arranged between the first end T4 of the fourth power conversion module 106 and the rechargeable battery BT. The second end T4' of the fourth power conversion module 106 is configured to be electrically connected to the DC bus DC. The power converter according to the embodiment of the present invention is configured to implement different operating modes, including a mains mode and a battery mode. When the mains is normal, control the operating logic of the first to third power conversion modules 101-103 and the switching logic of the first and second switch modules 104-105, so that the first ends of the first to third power conversion modules 101-103 all draw power from the mains, perform AC-DC conversion respectively and then supply it to their second ends, and then supply power to the load. At this time, if the rechargeable battery BT is undercharged, the fourth power conversion module 106 draws power from the DC bus to charge the rechargeable battery BT; when the rechargeable battery BT is fully charged, the fourth power conversion module 106 does not work. When the mains fails, control the operating logic of the first and second power conversion modules 101 and 102 and the switching logic of the first switch module 104, so that the first and second power conversion modules 101 and 102 jointly perform DC-DC conversion on the output of the rechargeable battery BT to supply power to the DC bus DC. In this way, when the mains fails, the rectification module is reused as a battery conversion module to supply power to the load by the battery, avoiding the idle of the rectification module, improving the utilization rate of the circuit, and saving the volume and cost of the power converter.At this time, preferably, the operating logic of the third power conversion module 103 and the switching logic of the third switching module 105 are controlled such that the third power conversion module 103 serves as a balancing branch for achieving the balance of the DC bus DC. In this way, there is no need to set up a dedicated balancing circuit, further improving the utilization rate of the circuit and further saving the volume and cost of the power converter. More preferably, the fourth power conversion module 106 also serves as a battery conversion branch to implement the DC-DC conversion from the rechargeable battery BT to the DC bus, greatly improving the battery power supply efficiency and reducing the full-load rate of the battery bridge arm. Usually, only a design with a full-load rate of about 50% is required, significantly reducing the cost and volume.

[0033] Refer to Figure 2 the circuit topology of the power converter according to an embodiment of the present invention as shown, which is configured to be electrically connected to a three-phase AC power supply AC and a DC power supply (such as a rechargeable battery) BAT. Figure 2 The circuit topology shown includes four bridge arms. The bridge arms L1-L3 are rectifier bridge arms, and the bridge arm L4 is a bidirectional DC / DC conversion bridge arm. Specifically, in this embodiment, the bridge arm L1 is a type-I three-level circuit, the bridge arms L2 and L3 are respectively dual-boost circuits, and the bridge arm L4 is a bidirectional DC / DC conversion circuit.

[0034] As Figure 2 shown, the type-I three-level circuit of the first bridge arm L1 includes the first to fourth transistors T1a, T2a, T3a, and T4a connected in series in sequence, the first and second diodes D1a and D2a connected in series with each other, and the first inductor La. Among them, the first end of the first transistor T1a is electrically connected to the positive DC bus DC+, the node between the second end of the first transistor T1a and the first end of the second transistor T2a is connected to the negative electrode of the first diode D1a, the node between the second end of the second transistor T2a and the first end of the third transistor T3a is connected to the first end of the first inductor La, the node between the second end of the third transistor T3a and the first end of the fourth transistor T4a is connected to the positive electrode of the second diode D2a, the second end of the fourth transistor T4a is electrically connected to the negative DC bus DC-, the node between the positive electrode of the first diode D1a and the negative electrode of the second diode D2a is grounded, the second end of the first inductor La is electrically connected to the first phase R of the three-phase AC power supply AC through the relay K1, the node between the relay K1 and the first inductor La is grounded through the relay K8, and the node between the relay K1 and the first phase R of the three-phase AC power supply AC is grounded through the capacitor C1. In addition, anti-parallel diodes are respectively built in the first to fourth transistors T1a-T4a.

[0035] The dual-boost circuit of the second bridge arm L2 includes a first to a fourth diode D1b - D4b connected in series in sequence, a first and a second transistor T1b and T2b connected in series with each other, and a second inductor Lb. Among them, the negative electrode of the first diode D1b is electrically connected to the positive DC bus DC+, the positive electrode is electrically connected to the first end of the first transistor T1b and the negative electrode of the second diode D2b, the positive electrode of the second diode D2b is electrically connected to the first end of the second inductor Lb and the negative electrode of the third diode D3b, the positive electrode of the third diode D3b is electrically connected to the second end of the second transistor T2b and the negative electrode of the fourth diode D4b, the positive electrode of the fourth diode D4b is electrically connected to the negative DC bus DC-, the node between the second end of the first transistor T1b and the first end of the second transistor T2b is grounded, and the second end of the second inductor Lb is connected to the second phase S of the three-phase AC power supply AC through a relay K2 and is connected to the positive electrode of the battery BAT through a relay K4. Similarly, anti-parallel diodes are built in the first transistor T1b and the second transistor T2b. It can be clearly seen from Figure 2 that the diodes D1b and D2b and the transistor T1b constitute the upper bridge arm unit of the second bridge arm L2, and the diodes D3b and D4b and the transistor T2b constitute the lower bridge arm unit of the second bridge arm L2.

[0036] The dual-boost circuit of the third bridge arm L3 includes a first to a fourth diode D1c - D4c connected in series in sequence, a first and a second transistor T1c and T2c connected in series with each other, and a third inductor Lc. Among them, the negative electrode of the first diode D1c is electrically connected to the positive DC bus DC+, the positive electrode is electrically connected to the first end of the first transistor T1c and the negative electrode of the second diode D2c, the positive electrode of the second diode D2c is electrically connected to the first end of the third inductor Lc and the negative electrode of the third diode D3c, the positive electrode of the third diode D3c is electrically connected to the second end of the second transistor T2c and the negative electrode of the fourth diode D4c, the positive electrode of the fourth diode D4c is electrically connected to the negative DC bus DC-, the node between the second end of the first transistor T1c and the first end of the second transistor T2c is grounded, and the second end of the third inductor Lc is connected to the third phase T of the three-phase AC power supply AC through a relay K3 and is connected to the negative electrode of the battery BAT through a relay K6. Similarly, anti-parallel diodes are built in the first transistor T1c and the second transistor T2c. Similarly, the diodes D1c and D2c and the transistor T1c constitute the upper bridge arm unit of the third bridge arm L3, and the diodes D3c and D4c and the transistor T2c constitute the lower bridge arm unit of the third bridge arm L3.

[0037] The bidirectional DC / DC conversion circuit of the fourth bridge arm L4 includes the first to third transistors T1-T3, and the first and second inductors Ld and Le. Among them, the first end of the first transistor T1 is electrically connected to the positive DC bus DC+, the node between the second end of the first transistor T1 and the first end of the second transistor T2 is connected to the first end of the first inductor Ld, the node between the second end of the second transistor T2 and the first end of the third transistor T3 is connected to the first end of the second inductor Le, the second end of the third transistor T3 is electrically connected to the negative DC bus DC-, the second end of the first inductor Ld is electrically connected to the positive electrode of the battery BAT through the relay K5, the second end of the second inductor Le is electrically connected to the negative electrode of the battery BAT through the relay K7, and the two ends of the battery BAT are connected in parallel with a filter capacitor C4. Similarly, anti-parallel diodes are built into the first to third transistors T1-T3.

[0038] A capacitor C2 and a capacitor C3 are connected in series between the output terminals of the second phase S and the third phase T of the three-phase AC power supply AC, and the node between the two capacitors is grounded.

[0039] A first capacitor Cp and a second capacitor Cn are connected in series between the positive DC bus DC+ and the negative DC bus DC-, and the node between the first capacitor Cp and the second capacitor Cn is grounded.

[0040] In the embodiment of the present invention, the dual-boost circuit of the second bridge arm and the third bridge arm L2 uses fewer transistors than the type-I three-level circuit of the first bridge arm L1, reducing the volume and saving costs.

[0041] The following combines Figure 3 and Figure 4 to discuss Figure 2 the working modes of the power converter shown.

[0042] Mains mode (mains working normally), as Figure 3 shown, the relays K1, K2, K3 are closed, and the relays K8, K4, K6 are open.

[0043] When the mains voltage is in the positive half-cycle, in particular, the voltage of each phase of the three-phase AC power supply AC is in the positive half-cycle:

[0044] For the first rectifier bridge arm L1, when T3a is turned on and T1a, T2a, and T4a are turned off, the first inductor La stores energy. The current path is: AC(R)→K1→La→T3a→D2a→neutral line N (grounded), as Figure 3 shown by the solid arrow.

[0045] After energy storage is completed, T1a, T2a, T3a, and T4a are turned off, and inductor La will release energy to DC link capacitors Cp and Cn. The current path is: La → D(T2a) → D(T1a) → DC+ → Cp → neutral line N (grounded), as shown by the dashed arrow in Figure 3 . This process is actually the process of inductor freewheeling after the transistor is turned off.

[0046] For the second rectifier bridge arm L2, when T1b is turned on and T2b is turned off, the second inductor Lb stores energy. The current path is: AC(S) → K2 → Lb → D2b → T1b → neutral line N (grounded).

[0047] After energy storage is completed, T1b and T2b are turned off, and inductor Lb will release energy to DC link capacitors Cp and Cn. The current path is: Lb → D2b → D1b → DC+ → Cp → neutral line N (grounded). This process is also the process of inductor freewheeling after the transistor is turned off.

[0048] Similarly, for the third bridge arm L3, when T1c is turned on and T2c is turned off, the third inductor Lc stores energy. The current path is: AC(T) → K3 → Lc → D2c → T1c → neutral line N (grounded).

[0049] After energy storage is completed, T1c and T2c are turned off, and inductor Lc will release energy to DC link capacitors Cp and Cn. The current path is: Lc → D2c → D1c → DC+ → Cp → neutral line N (grounded). This process is the process of inductor freewheeling after the transistor is turned off. For clarity, the current paths for the second bridge arm L2 and the third bridge arm L3 are not shown in Figure 3 .

[0050] When the mains voltage is in the negative half cycle, in particular, the voltage of each phase of the three-phase AC power supply AC is in the negative half cycle:

[0051] For the first rectifier bridge arm L1, when T2a is turned on and T1a, T3a, and T4a are turned off, the first inductor La stores energy. The current path is: neutral line N (grounded) → D1a → T2a → La → K1 → AC(R).

[0052] After energy storage is completed, when T1a, T2a, T3a, and T4a are turned off, inductor La will release energy to DC link capacitors Cp and Cn. The current path is: neutral line N (grounded) → Cn → DC- → D(T4a) → D(T3a) → La. This process is actually the process of inductor freewheeling after the transistor is turned off.

[0053] For the second rectifier leg L2, when T2b conducts and T1b is off, the second inductor Lb stores energy. The current path is: neutral line N (grounded) → T2b → D3b → Lb → K2 → AC(S).

[0054] After the energy storage is completed, T1b and T2b are turned off, and the inductor Lb will release energy to the DC link capacitors Cp and Cn. The current path is: neutral line N (grounded) → Cn → DC- → D4b → D3b → Lb. This process is also the process of inductor freewheeling after the transistor is turned off.

[0055] Similarly, for the third leg L3, when T2c conducts and T1c is off, the third inductor Lc stores energy. The current path is: neutral line N (grounded) → T2c → D3c → Lc → K3 → AC(T).

[0056] After the energy storage is completed, T1c and T2c are turned off, and the inductor Lc will release energy to the DC link capacitors Cp and Cn. The current path is: neutral line N (grounded) → Cn → DC- → D4c → D3c → Lc. This process is also the process of inductor freewheeling after the transistor is turned off.

[0057] In addition, in the mains mode, when the battery BAT is undercharged, the relays K5 and K7 are closed, and the DC bus DC+ and DC- charge the battery BAT. When the transistors T1 and T3 conduct and the transistor T2 is off, the DC bus stores energy in the inductors Ld and Le. The current path is: DC+ → T1 → Ld → K5 → BAT → K7 → Le → T3 → DC-; after the energy storage is completed, the transistors T1 and T3 are turned off, the transistor T2 conducts, and the inductors Ld and Le release energy. The current path is: Ld → K5 → BAT → K7 → Le → T2, continuing to charge the battery BAT. This process is also the process of inductor freewheeling.

[0058] In the battery mode (mains failure), the power converter is disconnected from the mains AC and is powered only by the battery BAT. As Figure 4 shown, the relays K8, K4, K6 are closed, and the relays K1, K2, K3 are open.

[0059] When T1b and T2c conduct and T2b and T1c are off, the inductors Lb and Lc will store energy. The current path is:

[0060] BAT+ → K4 → Lb → D2b → T1b → T2c → D3c → Lc → K6 → BAT-, as Figure 4 shown by the solid arrows.

[0061] When T1b, T2b, T1c, and T2c are all off, the inductors Lb and Lc will release energy. The current path is:

[0062] BAT+ → K4 → Lb → D2b → D1b → DC+ → Cp → Cn → DC- → D4c → D3c → Lc → K6 → BAT-, as Figure 4 shown by the dashed arrow in

[0063] In this way, the power supply from the battery BAT to the DC bus is realized. The second arm L2 and the third arm L3 together (for example, through the upper arm unit of the second arm L2 and the lower arm unit of the third arm L3) realize the DC-DC conversion, improving the utilization rate of the circuit.

[0064] Generally, all loads cannot be completely balanced. Particularly for a three-phase power supply, if only single-phase loads are connected, it will be very unbalanced. At this time, it is necessary to control the balance of the positive and negative DC buses. In the battery mode, preferably, the type-I three-level circuit of the first arm L1 is used as the balancing branch. By controlling its transistors to conduct alternately, the balance of the DC bus can be achieved. Specifically, if the voltage of the capacitor Cp is higher than the voltage of the capacitor Cn, when the transistors T1a and T2a are conducting and the transistors T3a and T4a are off, the inductor La stores energy, and the current path is: DC+ → T1a → T2a → La → K8 → neutral line (ground line) → Cp, as Figure 4 shown by the solid arrow in Figure 4 When the energy storage of La is completed, the transistors T1a and T2a are turned off, and the transistors T3a and T4a are turned on. La freewheels to release energy, and the current path is: neutral line (ground line) → Cn → DC- → T4a → T3a → La → K8, as Figure 4 shown by the dashed arrow in

[0065] In addition, considering that the rectifier bridge arm is reused as the battery conversion bridge arm, a switch needs to be switched, which takes time. Generally, the switching time is on the order of 10 ms, such as 20 ms. To ensure the continuity of power supply, in the battery mode, the battery also performs DC-DC conversion through the fourth bridge arm L4 to supply power to the DC bus. Specifically, the relays K5 and K7 are closed,

[0066] When T1 and T3 are turned off and T2 is turned on, the inductors Ld and Le will store energy. The current path is: BAT+ → K5 → Ld → T2 → Le → K7 → BAT-.

[0067] When T2 is turned off and T1 and T3 are turned on, the capacitor C4 and the inductors Ld and Le will release energy. The current path is: BAT+ → K5 → Ld → D(T1) → DC+ → Cp → Cn → DC- → D(T3) → Le → K7 → BAT-.

[0068] In this way, the battery BAT supplies power to the DC bus through the second bridge arm, the third bridge arm, and the fourth bridge arm together, greatly improving the battery power supply efficiency and reducing the full-load rate of the battery bridge arm. Usually, only about 50% of the full-load rate design is required, significantly reducing the cost and volume. Preferably, in this working mode, the fourth bridge arm is interleaved and paralleled with the multiplexed battery bridge arm formed by the second bridge arm and the third bridge arm, reducing the ripple. More preferably, the power converter according to the embodiment of the present invention is further provided with another battery bridge arm, as Figure 3 shown by the dotted line below the T phase in the figure. Multiple battery bridge arms are interleaved and paralleled to supply power to the DC bus, further reducing the ripple current.

[0069] In addition, the power converter according to the embodiment of the present invention also solves the disadvantage that the battery of the existing double-boost circuit needs to be provided with a neutral line. In the double-boost circuit of the prior art, the positive and negative electrodes of the battery have independent paths during discharge. In order to balance the positive and negative DC buses in the battery mode, a neutral line needs to be drawn from the midpoint of the battery pack, and the number of batteries connected in series must be even, and the number of transistors must also be increased. The embodiment of the present invention reuses the first bridge arm L1 as the balancing bridge arm, which can balance the positive and negative DC buses in the battery mode, has no requirement for the number of batteries, does not limit the on-site application, and reduces the cost.

[0070] Another embodiment of the present invention provides a UPS. Refer to Figure 5 the structural block diagram of the UPS of this embodiment shown in the figure. It includes a power converter 501, an inverter 502, a battery charging module 503, and a battery module 504. Compared with the traditional UPS, the power converter 701 of the UPS of this embodiment can perform DC-DC conversion on the output of the battery module 504 and then provide it to the DC bus, omitting a dedicated battery conversion module, reducing the volume of the UPS and saving costs.

[0071] Another embodiment of the present invention provides another UPS. Refer to Figure 6 the structural block diagram of the UPS of this embodiment shown in the figure. It includes a power converter 601, an inverter 602, a battery charging module 603, a battery module 604, and a battery conversion module 605. Compared with the traditional UPS, the UPS of this embodiment can use both the battery conversion module 605 and the power converter 601 to realize the power supply from the battery module 604 to the DC bus, improving the battery power supply efficiency. Preferably, the battery charging module 603 and the battery conversion module 605 are replaced by a bidirectional DC-DC conversion module, reducing the volume of the UPS and saving costs.

[0072] Since the power converter of the embodiment of the present invention can achieve different working modes by controlling the switches, the UPS according to the embodiment of the present invention can directly convert the battery output by the rectifier bridge arm or the battery conversion bridge arm to supply power to the DC bus under low load, and convert the battery output by both the rectifier bridge arm and the battery conversion bridge arm to supply power to the DC bus under high load. Therefore, the application scenarios of the UPS of the present invention are more extensive.

[0073] According to other embodiments of the present invention, the relay can be replaced by other switching elements well-known in the art, such as mechanical switches, circuit breakers, etc. In addition, the switch assemblies (K1, K8), (K2, K4), and (K3, K6) can be replaced by single-pole double-throw switches.

[0074] According to other embodiments of the present invention, the transistor is an IGBT, a MOSFET, etc.

[0075] According to other embodiments of the present invention, the first to third switch modules form a switch unit.

[0076] Although the present invention has been described by way of preferred embodiments, the present invention is not limited to the embodiments described herein. Various changes and variations are also included without departing from the scope of the present invention.

Claims

1. A power converter, comprising: The first power conversion module, which can be configured to implement AC-DC conversion, the first end of the first power conversion module is configured to be electrically connected to the first phase or the neutral line of the three-phase power supply, and the second end is configured to be electrically connected to the DC bus; The second power conversion module, which can be configured to implement AC-DC conversion, the first end of the second power conversion module is configured to be electrically connected to the second phase of the three-phase power supply or the rechargeable battery, and the second end is configured to be electrically connected to the DC bus; and The third power conversion module, which can be configured to implement AC-DC conversion, the first end of the third power conversion module is configured to be electrically connected to the third phase of the three-phase power supply or the rechargeable battery, and the second end is configured to be electrically connected to the DC bus; The switch unit is configured to selectively electrically connect the first end of the first power conversion module to the first phase or the neutral line of the three-phase power supply, the first end of the second power conversion module to the second phase of the three-phase power supply or the positive electrode of the rechargeable battery, and the first end of the third power conversion module to the third phase of the three-phase power supply or the negative electrode of the rechargeable battery, wherein the second power conversion module, the third power conversion module and the switch unit are configured to be able to perform DC-DC conversion on the direct current output by the rechargeable battery through both the second power conversion module and the third power conversion module and supply it to the DC bus, and balance the positive and negative electrodes of the DC bus through the first power conversion module.

2. The power converter according to claim 1, wherein, The second power conversion module and the third power conversion module respectively include an inductor, an upper bridge arm unit and a lower bridge arm unit, and are configured to perform DC-DC conversion through the upper bridge arm unit of the second power conversion module and the lower bridge arm unit of the third power conversion module.

3. The power converter according to claim 2, wherein, The first power conversion module is a type-I three-level circuit, and the second power conversion module and the third power conversion module are double-boost circuits.

4. The power converter according to claim 3, wherein, The double-boost circuit includes a first to a fourth diode connected in series in sequence, a first and a second transistor connected in series with each other, and an inductor. The negative electrode of the first diode is electrically connected to the positive electrode of the DC bus, the node between the positive electrode of the first diode and the negative electrode of the second diode is electrically connected to the first end of the first transistor, the node between the positive electrode of the second diode and the negative electrode of the third diode is electrically connected to the first end of the inductor, the node between the positive electrode of the third diode and the negative electrode of the fourth diode is electrically connected to the second end of the second transistor, the positive electrode of the fourth diode is electrically connected to the negative electrode of the DC bus, the node between the second end of the first transistor and the first end of the second transistor is electrically connected to the neutral line, and the second end of the inductor is electrically connected to the three-phase power supply or the rechargeable battery through the switch unit.

5. The power converter according to claim 3, wherein, The type-I three-level circuit includes a first to a fourth transistor connected in series in sequence, a first and a second diode connected in series with each other, and an inductor. Among them, the first end of the first transistor is electrically connected to the positive pole of the DC bus, the node between the second end of the first transistor and the first end of the second transistor is electrically connected to the negative pole of the first diode, the node between the second end of the second transistor and the first end of the third transistor is electrically connected to the first end of the inductor, the node between the second end of the third transistor and the first end of the fourth transistor is electrically connected to the positive pole of the second diode, the second end of the fourth transistor is electrically connected to the negative pole of the DC bus, the node between the first diode and the second diode is electrically connected to the neutral line, and the second end of the inductor is electrically connected to the three-phase power supply or the neutral line through the switching unit.

6. The power converter according to claim 1, wherein, The output terminals of the first phase, the second phase, and the third phase of the three-phase power supply are respectively grounded through capacitors.

7. The power converter according to claim 1, further comprising a fourth power conversion module, which can be configured to implement DC-DC conversion, a first end of the fourth power conversion module is configured to be electrically connected to the rechargeable battery, and a second end is configured to be electrically connected to the DC bus.

8. The power converter according to claim 7, wherein, The first end of the fourth power conversion module is electrically connected to the rechargeable battery through the switching unit.

9. The power converter according to claim 7 or 8, wherein, The fourth power conversion module is a bidirectional DC-DC circuit.

10. An uninterruptible power supply, comprising: The power converter according to any one of claims 1-9 An inverter, which is electrically connected to the DC bus of the power converter; and A rechargeable battery, whose output terminal is electrically connected to the switching unit of the power converter.

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